1. Field of the Invention
The present invention relates to a method, system, and program for synchronizing data.
2. Description of the Related Art
Many small mobile devices, such as hand held computers, Personal Digital Assistants (PDAs), etc., utilize the SyncML synchronization protocol to synchronize data at a remote central server. Handheld computers, mobile phones, pagers, laptops, Personal Digital Assistant (PDA), etc., may synchronize their data with network applications, desktop calendars, and other locations where information is stored. This ability to readily access and synchronize information is key to the pervasive nature of mobile computing.
Occasionally, conflicts may need to be resolved between the data at the remote devices and the central data location, or server. Mobile device users may retrieve data from the network and store the data on the mobile device, where they access and manipulate the local copy of the data. Periodically, users reconnect with the network to send any local changes back to the networked data repository. Users also have the opportunity to learn about updates made to the networked data while the device was disconnected. Occasionally, they need to resolve conflicts among the updates made to the networked data and/or local copy of the data at the mobile device. This reconciliation operation where updates are exchanged and conflicts are resolved is known as data synchronization, where two sets of data are processed to make the two sets identical. For a mobile device, synchronization applies to the data that the mobile device stores locally.
In the SyncML protocol, a SyncML client, such as a mobile phone, pager, PDA, etc., sends modifications to data to a SyncML server. The SyncML server is responsible for performing the synchronization analysis when receiving client modifications. If for some reason, the client and server lose synchronization in a manner that results in errors or synchronize for the first time, either the server or client may initiate a slow synchronization (slow sync). Slow sync is a two-way synchronization in which all items in one or more database are compared with each other on a field-by-field basis. In the slow sync process, the client sends all its data in a client database stored in the client device to the server, and the server performs the sync analysis on a field-by-field basis between the received client data and the server data. After the slow sync analysis, the server returns all needed modifications back to the client. Further details of the slow sync and other synchronization methods are discussed in the publication “SyncML Sync Protocol, Version 1.1”, (February 2002), available at www.syncml.org, which publication is incorporated herein by reference in its entirety.
Because a slow sync operation requires an analysis of every record in a database as maintained at a client and server on a field-by-field basis, the slow sync process can take a considerable amount of time and consume significant network bandwidth resources to transfer all records in the database. Network bandwidth and transmission time is even more crucial for wireless networks where the transmission bandwidth is significantly less than that of a high speed transmission line based network.
Accordingly, there is a need in the art for improved techniques for synchronizing data between clients and servers.